Apple didn't include its market share in the release, but Ars reported that Apple had 19 percent of overall music sales in the U.S. during January, compared with Wal-Mart's 16 percent. Apple did say that its achievement was based on two months of data, from sales in January and February of this year.

One interesting note about NPD's MusicWatch survey is that it equates 12 tracks with the sale of one CD. iTunes generates a lot of one- or two-track purchases as compared with the purveyors of physical CDs, where you either buy the whole thing or you don't. All those 99-cent transactions apparently add up.

About the author

Tom Krazit writes about the ever-expanding world of Google, as the most prominent company on the Internet defends its search juggernaut while expanding into nearly anything it thinks possible. He has previously written about Apple, the traditional PC industry, and chip companies. E-mail Tom.
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